Abstract
Large-area graphitic films, produced by an advantageous technique based on spraying a graphite lacquer on glass and low-density polyethylene (LDPE) substrates were studied for their thermoresistive applications. The spray technique uniformly covered the surface of the substrate by graphite platelet (GP) unities, which have a tendency to align parallel to the interfacial plane. Transmission electron microscopy analysis showed that the deposited films were composed of overlapped graphite platelets of different thickness, ranging from a few tens to hundreds of graphene layers, and Raman measurements provided evidence for a good graphitic quality of the material. The GP films deposited on glass and LDPE substrates exhibited different thermoresistive properties during cooling–heating cycles in the −40 to +40 °C range. Indeed, negative values of the temperature coefficient of resistance, ranging from −4 × 10−4 to −7 × 10−4 °C−1 have been observed on glass substrates, while positive values varying between 4 × 10−3 and 8 × 10−3 °C−1 were measured when the films were supported by LDPE. These behaviors were attributed to the different thermal expansion coefficients of the substrates. The appreciable thermoresistive properties of the graphite platelet films on LDPE could be useful for plastic electronic applications.
Highlights
Plastic electronics is an emerging technological field with a remarkable potential in the areas of robotics, solar energy, sensors, health care, industrial automation, etc. [1,2,3,4,5]
The Graphit 33 was sprayed in acetone, the solid phase was isolated by centrifugation and deposited on a transmission electron microscopy (TEM) copper grid covered with a thin carbon film
Uniform intensity that could be correlated to the platelet’s tendency to align, in average, parallel to Spectra analysis of graphite platelet (GP) films deposited both on glass and low-density polyethylene (LDPE) substrates indicated that the the interfacial plain
Summary
Plastic electronics is an emerging technological field with a remarkable potential in the areas of robotics, solar energy, sensors, health care, industrial automation, etc. [1,2,3,4,5]. The surfaces of polymers such as poly (methyl methacrylate), polyethylene terephthalate and low-density polyethylene (LDPE) have been made conductive by depositing graphite or graphene layers onto them for the fabrication of printed radio frequency devices [18], electrically conductive paths [19], piezoresistive sensors [20], and strain gauges [9] These layers can be deposited by chemical vapor deposition [21], casting and drying inks [18], micromechanical techniques based on spreading an alcoholic suspension of graphite nanoplatelets [22,23] and spraying conductive composites [9]. Owing to the thermal expansion coefficient mismatch, the substrate could dramatically affect the temperature coefficient of resistance (TCR) of the GP film, which exhibited a negative TCR on glass and a positive TCR on the LDPE substrate
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